How is a Sound Loud or Soft?

Once again, I used World Book to help me. The section I used is here. Essentially, the subsection explained that the intensity of the sound is due to the sound's amplitude, or the longest distance that an object moves from its position of rest as it vibrates. If the amplitude increases, the intensity of the sound increases. Sound intensity is measured in decibels (dB). The softest sound a human can hear is a 3,000 hertz tone of 0 dB. That is called the threshold of audibility. A level of 140 dB is the threshold of pain. Sounds of 140 dB or more can damage a person's eardrum. How strong the sound is is called loudness. The more intense a frequency is, the louder the frequency is. Loudness is measured in phons. Another "thank you" to World Book Student, and please reference "How Are Sound Waves Created?" for the work cited.